An increase in the use of state-of-the-art imaging techniques has led to the discovery of a greater number of small, incidentally discovered renal masses, benign and malignant. Up until now, current interventions in obtaining samples of the renal masses were limited to minimally invasive (e.g. needle biopsy) to standard surgical procedures. Currently, diagnosis of such masses for treatment decision making is limited to tests that rely on morphological analyses alone. However, such tests pose certain drawbacks. Two main limitations include: (i) the inability to obtain diagnostic material from minimally invasive procedures (e.g. needle biopsy) of adequate quantity and quality for morphological examination; and (ii) the inability to distinguish the predominant subtypes of renal cortical neoplasms morphologically.
Furthermore, a large proportion of patients with small, incidentally discovered renal masses are within an older, more frail population and for renal cell carcinoma (RCC), 60-70% of patients are asymptomatic. Thus, for patients with such masses, an alternative to invasive diagnostic methods, i.e., surgery, is required.
As such, there exists a need for a highly sensitive and specific molecular diagnostic method which does not require the use of surgery, and thus, does not require: (i) a large quantity of diagnostic material; and (ii) the use of standard pathological methods for classification and analysis. Indeed, applications, such as the present invention, that use samples obtained through minimally invasive procedures (e.g. needle biopsy) in order to detect and analyze changes on a molecular level are more likely to provide early detection than applications that rely on morphological analyses alone. And early detection of a specific disease state can greatly improve a patient's chance for survival by permitting early diagnosis and early treatment while the disease is still localized and its pathologic effects limited anatomically and physiologically.
Two key evaluative measures of any test or disease detection method are its sensitivity and specificity, which measure how well the test performs to accurately detect all affected individuals without exception, and without falsely including individuals who do not have the target disease. Historically, many diagnostic tests have been criticized due to poor sensitivity and specificity.
As such, this patent application describes an innovative, sensitive and specific molecular cytogenetic method-based detection test that is based on the inherent differential genetics of renal cortical neoplasms, and not on cell morphology.
The statistics with respect to kidney cancer in the United States are startling. In fact, in 2007, 51,190 Americans are expected to be diagnosed with kidney cancer and 12,890 are expected to die of the disease. Of these patients, 62% are male and 38% female. Overall, this represents approximately 3% of all cancers in the United States and comparatively the 7th most prevalent cancer in men and 8th in women (1).
Of all kidney cancers, renal cell carcinoma (RCC), arising in the cortex of the kidney, is the most common (90%), and is also the most lethal. The incidence of RCC has increased for the past 65 years by about 2% every year. The underlying cause for this is currently unknown. The median age at diagnosis of RCC is 65 years. Several risk factors for the disease have been identified and include both lifestyle (smoking and obesity) and hereditary factors. The most common hereditary type is that associated with von Hippel-Lindau disease (VHL), arising due to mutations in the VHL gene and is more often associated with young patients.
RCC is usually indicated as a suspicious mass involving the kidney that appears in a radiographic analysis such as a computed tomographic (CT) scan or in some cases ultrasound. In most cases, the scan is either performed in response to a symptomatic renal mass or for some other condition that incidentally lead to the detection of the lesion.
Following detection of a renal mass, an initial work-up is performed, including a thorough physical examination and a laboratory examination (complete blood cell count, comprehensive metabolic panel, coagulation profile, and urine analysis). Oftentimes, additional imaging analyses are necessary, including CT of the abdomen and pelvis (with and without contrast), and chest radiograph or CT scan of the chest or brain. In selected cases, an MRI may be used to determine vascular involvement of the inferior vena cava or the presence of brain metastases.
Next, depending on the clinical indications, recommendations for surgery or alternative therapies are provided. In the case of surgery, an understanding of the true pathology will not be obtained until several days after surgical resection. Needle biopsy is occasionally performed in the pre-treatment setting in those cases where risks of competing malignancies may exist, when a benign process is suspected, or prior to ablation procedures.
Historically, biopsy procedures for renal masses have been under-utilized due to prior studies showing diagnostic inaccuracy in using these small specimens for morphologic analysis. Although, as detailed below, more recent studies have indicated that preoperative renal biopsies play an important role in the clinical management of patients with radiological evidence for a renal mass. Thus, resulting in a need for the present invention.
It is also evident that using morphologic criteria alone to interpret biopsies is frequently “non-diagnostic” or can result in ambiguous interpretations due to the heterogeneous nature of these tumors. Thus, in an effort to overcome these issues, the present invention teaches that the biopsy specimen should be analyzed for the presence/absence of histologic subtype-specific genetic abnormalities to not only aid in differential diagnosis but also to improve the efficacy of preoperative biopsy.
The accurate identification of renal masses is of critical importance in all phases of clinical management of this disease. For patients with small lesions, an accurate diagnosis, which distinguishes between a benign and malignant lesion, would thus lead to the appropriate type of therapy. Thus, avoiding needless procedures being used on patients with benign lesions.
For patients with larger neoplasms, diagnosis of tumor subtypes would serve to stratify patients for their risks of local or regionally advanced disease that can be factored in to treatment selection recommendations (i.e., extent of surgical intervention, less invasive options or ablation).
In patients with metastatic disease, drug trials are currently based on post-surgical tumor diagnosis, causing 4-6 weeks in delay to potentially curative treatment while risking associated peri-operative complications, functional nephron loss, and convalescence-related quality of life changed for uncertain clinical benefit.
As defined herein, renal cortical neoplasms are tumors or other abnormal growths that arise from the cells of the renal parenchyma (the tissue that constitutes the essential or functional part of the kidney).
These neoplasms are morphologically classified as shown in Table 1. Both benign and malignant lesions are shown in Table 1 with the most common benign lesion, oncocytoma (OC), constituting 6-9% of renal cortical neoplasms. Of the malignant lesions, the most common subtype is clear cell RCC (ccRCC), followed by papillary RCC (pRCC), and chromophobe RCC (chRCC).
TABLE 1Classification of predomimant subtypes of renal cortical neoplasmsand frequently associated cytogenetic abnormalities.Frequent CytogeneticHistologic SubtypeFrequencyAbnormalityBenignOncocytoma (OC)6-9%Loss of chr1, chr14, Y;11q13 translocationPapillary adenoma<1%No consistent abnormalityidentifiedMetanephric adenoma<1%No consistent abnormalityidentifiedNephrogenic adenofibroma<1%No consistent abnormalityidentifiedMalignantClear cell (conventional) 60-65%Loss of 3p, 3q, 9p21,RCC (ccRCC)chr14, Y; gain of 5Papillary RCC (pRCC)13-15%Gain of 3q, chr7, 17; loss of YChromophobe RCC (chRCC) 6%Loss of chr1, 2, 6, 10,13, 17, 21, YCollecting duct carcinoma<1%Loss of chr1, 6, 14, 15,22; gain of chr3Medullary carcinoma<1%No consistent abnormalityidentifiedTubulocystic RCC<1%No consistent abnormalityidentifiedRCC, unclassified 7%Mucinous tubular and spindle cell<1%Loss of chr1, 4, 6, 8, 13,carcinoma14Translocation-associated carcinomas<1%Xp11.2 translocationTumors of undetermined malignant potentialMultilocular cystic RCC<1%No consistent abnormalityidentified
The identification of cytogenetic abnormalities consistently associated with the subtypes of renal cortical neoplasms have allowed the classification of RCC more precisely (Table 1) (3-11). The probe panel of the present invention was designed to take into account the single abnormalities that define a subtype, along with the secondary and complex abnormalities that together allow a more precise classification. These abnormalities also provide molecular clues to the underlying genetic basis of the disease. This is exemplified by the consistent loss of 3p25 in ccRCC which along with mutation analysis has indicated a role for the VHL locus even in sporadic ccRCC (12, 13).
Prior to applicants' invention, there were no probes which could accurately detect the type of renal cortical neoplasm present in a renal biopsy sample. Moreover, applicants' invention does not require large quantities of diagnostic material since the claimed probes are highly sensitive.
Thus, for the first time, accurate detection and analysis of the type of renal cortical neoplasm may be performed on a biopsy sample obtained using non-invasive methods.
As noted above, the present invention is directed to a novel molecular cytogenetic method-based probe panel which detects the type of renal cortical neoplasm present in a renal biopsy sample. As such, the invention permits diagnosis of the four predominant subtypes of renal cortical neoplasms without surgery.